LI+ battery charger with thermal regulation
Description
The STBC21 is a constant current/constant voltage charger for single cell Li-Ion batteries.
Most of the charging parameters, including floating voltage, pre-charge and termination current are programmable in NVM memory. While fast charging current is programmed using an external resistor. The constant current process is split into three phases depending on the battery voltage. If the battery voltage is below 3.0 V, the charging current is set to a programmable value below 200 mA. A timeout of 60 minutes is used in this phase to detect faulty batteries. When the battery voltage goes above 3.0 V, the charger moves to the fast-charge procedure with a current programmable by an external resistor up to 1.1 A.
When the battery reaches the value of the floating voltage the charger enters “constant voltage” mode. Even in this mode a protection timer is active to avoid risks due to damaged batteries.
The charge cycle is automatically terminated when the current flowing to the battery reaches the value programmed in NVM. There is also a programmable lag time after the termination to maximize the battery charge. An internal block regulates the battery floating voltage when its temperature is outside the safety range between 10 °C and 45 °C, (JEITA/PSE regulation). The floating voltage inside the safety range is set, by default, at 4.2 V. If the external power supply is removed, the STBC21 turns off and a 50 µA (max.) current can flow from the battery to the device. The device also has an undervoltage lockout and automatic recharge capability which can be enabled/disabled by setting a bit in NVM.
Two separate status pins allow a lot of information to be gotten based also on flashing frequency and duty cycle. The STBC21 also includes a reversed battery polarity protection to prevent damage due to incorrect battery insertion. The package is a HTSSOP-14 (5 x 4.4).
Features
■ Programmable charge current up to 1.1 A
■ Floating voltage limitation outside the safety temperature range
■ PSE fully compatible
■ Low battery voltage detection for pre-charge setting
■ Automatic recharge
■ Two charge status output pins
■ Constant current / constant voltage operation
■ No external MOSFET, sense resistors or blocking diode required
■ Reverse current blocking (50 µA max.)
■ Short-circuit protection and thermal shutdown
■ Less than 1 mA supply current in standby mode
■ Reversed battery polarity protection
■ I²C interface for charging parameters programming
■ ESD: HBM ± 2 kV, CDM 500 V on every pin
■ HTSSOP-14 (5 x 4.4 mm) package available
■ -25 °C to 125 °C operative junction temperature
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